30 Bulletin 47, United States National Museum. 



This genus is very close to Mustclus, with which it agrees in most ex- 

 ternal respects, the essential difference being in the presence of a placenta 

 connecting the embryo with the uterus. The teeth are rather sharper 

 than in Hustelus. The boundaries of this group and the preceding are 

 not yet well denned, and it may be that the two should be reunited. 

 , a kind of shark, like yaAjjj, the weasel.) 



a. Middle ot first dorsal about midway between posterior root of pectorals and anterior root 

 of ventrals; first dorsal longer tluiu high ; its tip not reaching tip of posterior lobe, its free 

 margin scarcely incised, its base about half the interval between dorsals; teeth sharpish. 

 (Embryo not examined.) DORSALIS, 32. 



aa. Middle of first dorsal much nearer root of ventrals than pectorals; snout rather short, its 

 length from mouth a little less than distance between angles of mouth; teeth rather 

 sharp. CALIFORNICUS, 33. 



32. GALEUS DORSALIS, (Gill). 



Lower lobe of caudal not acute ; tail less than total length, its terminal 

 lobe less than i its length ; pectorals obtuse, their free edges almost 

 straight, their tips reaching first fourth of dorsal ; inner lobe of ventrals 

 not produced, the free edge of the fin straight. Embryo with placenta. 

 Color dark gray, axils of pectorals and ventrals dusky. L. 3 to 4 feet. 

 Panama and neighboring waters, north to the Gulf of California, the 

 largest species of the group, (dorsalis, pertaining to the back.) 



Mustelw dorsalis, GILL, Proc. Ac. Nat. Sci. Phila., 1864, 149, Panama. 

 Mwstelus dorsalis, JORDAN & GILBERT, Proc. U. S. Nat. Mus., 1882, 110. 



33. GALEUS CALIFORNICUS, (Gill). 



First dorsal longer than high, its blunt tip when depressed not reaching 

 tip of posterior lobe, its margin deeply incised, its base 2 times in the 

 interval between dorsals j lower lobe of caudal blunt ; terminal lobe of 

 tail more than its length, pectorals rather obtuse, their free margin 

 little concave, their tips reaching little past front of dorsal ; inner lobe of 

 ventrals somewhat produced ; embryo attached to uterus by a placenta. 

 Dark grayish ; axils of pectorals and ventrals dusky. L. 30 inches. Cali- 

 fornia, north to San Francisco; rather common. 



Muslelus californicus, GILL, Proc. Ac. Nat. Sci. Phila., 1864, 148, San Francisco. 

 Mmlelus californicus, JORDAN & GILBERT, Proc. U. S. Nat. Mus., 1882, 110. 

 Mustelus californicus, JORDAN & GILBERT, Synopsis, 870, 1883. 



20. RHINOTRIACIS, Gill. 



Ithinotriacis, GILL, Proc. Ac. Nat. Sci. Phila., 1862, 486, (henlei). 



General appearance of Galeus, but with the teeth distinctly tricuspid 

 and not paved. Snout sharp. Embryo attached to the uterus by a 

 placenta. Coloration plain. One species known. (f)iv, snout; Triads'). 



they have been accepted by nearly all later authors. It seems to us best in cases like this to 

 follow the rules of nomenclature strictly. The strict letter of the law seems to require the use 

 of Galeus in place of Pleuracromylon. 



The name Mnsfelus was at first applied by Cuvier to the whole group of smooth-mouthed 

 sharks. It has, however, been restricted by Gill to the subgenus typified by Jf. cum*, and it 

 should be retained for this subdivision, leaving Pleuracromylon, or Galeus, as the name of the 

 other genus or subgenus. 



